Not at all surprised this is getting downvoted. There's a decent book on this theme:

https://www.amazon.com/Hallucinations-Oliver-Sacks/dp/030794...

where the author postulates that a decent portion of society experiences hallucinations at least once in their lifetime without any "helpers" like drugs or sleep deprivation. (I don't remember the exact percentage, read that thing ages ago).

I think this is how religions get started.

If you haven't read it, you should check out Hallucinations, by the neurologist Oliver Sacks. His books in general are super fascinating, but there's a really interesting section on drugs in that one, and specifically mentions psychedelics a number of times (which isn't a shock considering it's a book on hallucinations).

http://www.amazon.com/Hallucinations-Oliver-Sacks/dp/0307957...